The setting of a cone crusher, that is, the "gap" between the mantle and the bowl liner, is typically adjusted in essentially one of two ways in those designs in which the bowl is moved relative to the head (as opposed to those in which the head is moved relative to the bowl, as in U.S. Pat. No. 3,873,037, for instance). Either the bowl and its liner are threaded into the bowl support and the bowl rotated relative to the bowl support to adjust the setting, as in U.S. Pat. Nos. 3,140,835; 3,420,457; and 3,454,230, for example, or the bowl support is simply moved rectilinearly vertically of the frame by hydraulic means, as in U.S. Pat. Nos. 2,791,383; 3,396,916; 3,604,640; and 3,754,716, for example, or by jack screws as in U.S. Pat. No. 3,337,143. Whichever approach is used, some means are also employed to "lock" the bowl to the bowl support in the former instances, or the bowl support to the crusher frame in the latter instances, in order further to resist crushing forces imposed upon the bowl and liner. In the former a threaded "locking ring" is typically used as in U.S. Pat. Nos. 3,140,835 and 3,420,457, the rings being hydraulically impelled. In the latter instances either the hydraulic adjusting means are in effect "locked up" as in U.S. Pat. No. 2,791,383 using double acting hydraulic cylinders, and/or an annular "wedge ring" made up of several segments is used as in U.S. Pat. Nos. 3,337,143; 3,604,640; and 3,754,716, the wedge rings being hydraulically actuated and operative between the bowl support and the crusher frame.
Nowadays the trend is more and more towards controlling operation of a cone crusher, including its setting, from a location remote from the crusher itself, such as a station from which an entire crushing plant, including feeders, screens, and so forth, is controlled. If the bowl is threaded into the bowl support and a hydraulically actuated locking ring is employed, remote adjustment is possible and is said to have been achieved but requires an elaborate and expensive system of hydraulic rams and pawls to rotate the bowl, as in U.S. Pat. No. 3,759,453. Furthermore, the adjustment can only be in finite steps, dependent upon the stroke of the rams, rather than infinite. Another difficulty in that instance is that remote operation demands some means at the crusher for accurately measuring and transmitting the crusher's setting. This is not easily provided both because the bowl must rotate to adjust the setting and because of the rather coarse nature of the buttress threads used between the bowl and its support. Nor can remote setting of a cone crusher in which the bowl support is moved relative to the frame be accomplished if shim stacks are employed, as in U.S. Pat. Nos. Re. 27,970 and 3,337,143, to adjust the setting. Obviously, then, the best solution is to move the bowl support relative to the frame using double acting hydraulic cylinders or the like interposed between the frame and the bowl support, and then "lock-up" the setting using hydraulically actuated clamps, since an all-hydraulic system lends itself more readily to remote control and to infinite and so more precise adjustment. The position of the liner relative to the mantle can then be measured by well-known means, such as the linear potentiometers shown in U.S. Pat. No. 3,754,716, for instance.
But an all-hydraulic system is beset with the problem of "creep", that is, a gradual increase in the setting when the crusher is operating under load. Even when fluid is "locked" on both sides of the pistons of the adjusting cylinders and even when in addition a wedge ring impelled by hydraulic clamp cylinders is used to clamp the bowl support relative to the frame, "creep" nevertheless occurs using fluid pressures in the adjust and clamp cylinders in the range of 3,000 psi which are typical of those supplied by the hydraulic pumps employed in crushing plants and the like. "Creep" ensues even at those pressures and despite the wedge ring because of system leakage and especially because of a certain amount of compression of the hydraulic fluid in the adjusting cylinders owing to movement of the bowl support relative to the frame despite the clamp of the wedge ring. This could probably be overcome by raising the clamp pressure on the wedge ring to, say, 10,000 psi, but that would require a prohibitively expensive pump as well as involve dangerously high line pressures.
Another aspect of the "creep" problem involves the overload system used to increase the setting temporarily should uncrushable matter such as tramp iron be introduced into the crusher. Such systems are independent of that used to adjust crushing setting and typically consist of springs, or hydraulic cylinders plus an accumulator as in U.S. Pat. No. Re. 27,970, interposed between the bowl and the bowl support such that the bowl can lift relative to the bowl support. Consequently, the hydraulic locking system of the crusher must be more powerful than the overload system so that passage of tramp iron, for instance, will only move the bowl relative to the bowl support but not the latter relative to the frame and thus disturb the setting. Hence not only must the locking system resist "creep" during normal crushing loads but also during the higher loads imposed upon it when the overload system operates to relieve the setting during passage of uncrushable material.
The primary object of the present invention is thus an improved all-hydraulic system for adjusting the setting of a cone crusher operable from a remote location, which system overcomes the "creep" problem.